CHRISTIAN Ribeiro has been forced into retirement aged just 27 after taking medical advice over a knee injury.

The full back was substituted with the issue earlier this month in the Checkatrade Trophy defeat to Milton Keynes Dons.

But he had been struggling with a problem in his left knee for several weeks and a scan showed up a problem which prompted a recommendation to hang up his boots.

Ribeiro said: “It has been really tough, the hardest decision I have ever had to make.

“But I have to do what is right in the long-term and therefore, sadly, I am going to have to hang up my boots.

“I have always given my all for the team throughout my career but unfortunately over the past couple of months since incurring an issue, I knew that something wasn’t right.

“I was playing in severe pain and really struggling to recover.

“The medical team here have been brilliant but eventually it got to the stage where I had to see a specialist and unfortunately the damage was worse than we had hoped.”

It is particularly tough for a player who endured a long rehabilitation from a separate issue which saw him spend almost the whole of last season in the treatment room.

Having joined from Exeter City in May 2016, Ribeiro broke an ankle in the final training session of pre-season.

Complications following the surgery delayed his debut until April and the Dons game was only his 17th appearance for the U’s.

United manager Pep Clotet said: “Slowly it has deteriorated and it has come to a moment where they made a new scan last week and the doctor was of the opinion he should not be playing football.

“This has never happened to me before and normally it doesn’t happen, especially at that age.

“Christian Ribeiro earned his right to be a footballer.

“He worked very hard for it and overcame really tough injuries.

“The fact he now has to put an end to his career because of a problem in his knee and a medical recommendation makes it really sad.

“It just shows how sometimes life is ruthless.”

In total he made 188 club appearances during a career which also saw him two senior caps for Wales.

Ribeiro is the third big injury blow which has hit the United squad in less than a fortnight, following serious injuries to fellow regulars Curtis Nelson and Rob Hall.